C410ax router, AP905 access points - external mesh options?

I've got a small set-up with a C410ax router and three AP905 access points. They're all connected via Ethernet and the mesh works well.

I've checked the Mesh compatibility page and their does not seem to be an external AP that will mesh with the C410ax and AP905s.

Is this the case or have I overlooked and option?

Assuming by "external" you mean "outdoor" then yes, you're right in saying that none of the compatibility lists show an outdoor AP that will mesh with those devices. However, is there actually any significant advantage in having the outdoor AP in a mesh, as opposed to straight AP mode?